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Case-IH Magnum suspended front axle settles and raises constantly


pirlbeck
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We have a customers Magnum 305 that came in for suspended front axle codes. We tracked the code problem down to a 6 inch length of the harness going to the suspended axle valve that all the wires were bare. Not sure what happened, because it looked like heat damage to the harness, but the harness does not run close to the exhaust system. Anyway, after repairing the harness damage and calibrating (it calibrated just fine) when we drive it the front end is raising itself and then creeping back down about every 5 to 10 seconds. It is most noticeable driving it slow on a smooth surface. When we drive it faster on a rough surface I think the normal action of the suspended axle prevents us from noticing the raising and settling.

We tried swapping the solenoid valves and it did not make a difference.

If we shut the tractor down with the axle cylinders extended, it does not settle to the stops, so we don't think it is a bad cylinder piston packing,

Looking for input if this could be normal or if we need to keep looking? Any help or suggestions appreciated.

Thanks!

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Wonder if it couldnt be the suspension accumulator needing charged up. Had one a few months ago that seemed to hunt for position all the time but no faults. Charged up the accumulator down by the left hand fuel tank and the problem went way.

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1 hour ago, 756puller said:

Wonder if it couldnt be the suspension accumulator needing charged up. Had one a few months ago that seemed to hunt for position all the time but no faults. Charged up the accumulator down by the left hand fuel tank and the problem went way.

Cant get a new one if you need it got a Mxm120 that needs the accumulator but can’t get it

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23 hours ago, Thesd5488 said:

Cant get a new one if you need it got a Mxm120 that needs the accumulator but can’t get it

How much different than boxcar accumulator ? 

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Pat, if I may ask, which suspended axle system does it have? IIRC, the Gen. III/Tier III Magnums had three different setups depending on the vintage of tractor. The first ones(think it was mainly the "MX" 215/245/275/305s that had this setup) used the piston pump to raise the axle and gravity to lower the axle...this axle was a holdover from the Gen II MX Magnums. Second style used 2 accumulators & used piston pressure for both raise & lower of the axle. The third style used just one accumulator and a different SFA valve. This system is still more or less the setup used on Tier IV Magnums.

The comments about checking accumulator charge pressure and making sure the linkage for the SFA pot is free are spot on. I also remember they were changing the software in the TMF controller for different operational characteristics of the SFA's performance...might want to make sure the TMF controller has the latest software.

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SDman,

This one has 2 accumulators in the front center of the tractor, but there is also an accumulator on the LH side, just forward of the LH fuel tank, close in next to the frame/housing. This accumulator has a steel line running across and tee's into a fitting at the front of the SFA valve.  So it looks to me like there are three accumulators that tie in the the SFA system. I also know Nate was able to view SFA piston and ram pressures in the trans view on the corner post.  From the info you provided above, I am guessing this may be the "middle" style.

The tractor SN is Z7RZ05451

We have looked at the SFA pot linkage and while we have not disconnected it, the lever and shaft will move in and out just a little bit with no apparent binding.

I do not think he has checked accumulator charge, but I thought Nate might of said something about seeing an accumulator charge pressure in the trans view menu......I am not sure how that would be possible, as I don't think there is any sort of sensor on the charge port end of the accumulator. We do have the equipment to check and charge the accumulators, so that and the pot linkage will be next on our list of things to try. We will also try to find out if the TMF software is up to date.

In your experience, what we are seeing with the front end raising and then settling you would not be consider it to be normal...is that correct?

Thanks a bunch!

Pat

 

 

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We removed the axle sensor pot, and the linkage is/was not binding. We ohm tested the pot and got some erratic readings so we replaced the sensor pot and lubricated the pot actuator shaft while we had it apart. We did run into something interesting with the 2 larger front accumulators when we took a look at them. They had Agco stickers on them and recommended charge pressure of 1985PSI, which is way over the Case-IH accumulator charge pressure of 856-899PSI and when we checked them they were charged in the 1700 + PSI range, so we lowered the pressure to the recommended pressures. 

The TMF controller software is ver. 2.10, the trans controller is ver. 2.8 and the arm controller is ver. 2.9. Would anyone know the latest versions of the available software. The tractor SN is Z7RZ05451

After changing the sensor pot and the accumulator pressures we calibrated the FSA which it did with no errors or faults. 

When test driving it, it still raises and lowers the front end, but it is not as abrupt in its movements. You can hear the hydraulics go on pressure and sometimes it appears to stay on pressure for several seconds or longer. One other thing is that the Suspended Front Axle switch on the control console does not seem to work as described in the owners manual. The switch light never comes on, the "Suspended Axle Locked" icon on the corner post display does not illuminate and it does not lock the axle in the mid position. The corner post icon will illuminate momentarily while it is doing the calibration routine, so it does work.

My gut feeling is that something is still not 100% correct, but we have never been around a red tractor with SFA so we don't have anything to compare it to. This tractor is new to this owner and first SFA tractor and his only complaint was the fault codes and the beeping from setting the codes.

Any thoughts?

Thanks!

 

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  • 10 months later...
On 5/4/2022 at 10:26 AM, Keith gabel said:

Pirlbeck did you ever get the front suspension figured out ? I have the exact same issues going on and getting sick of throwing $500 parts at it every other week 

We sent the tractor back out to the customers and have not heard any complaints back.  As I stated above, my gut feeling is that it is not 100% working correctly, but it was not real noticeable, so the customer my not even be aware it does this.

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On 6/25/2021 at 5:45 PM, CIHTECH said:

Hurry up and get it figured out as I have a MXM190 on the lot doing the same thing.

Did you ever get it figured out I’m desperate for help trying to figure this out , my local dealer is short handed and not much help at the moment 

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On 6/25/2021 at 10:22 PM, 756puller said:

Wonder if it couldnt be the suspension accumulator needing charged up. Had one a few months ago that seemed to hunt for position all the time but no faults. Charged up the accumulator down by the left hand fuel tank and the problem went way.

Did you pull the accumulator to charge it or do it on the tractor 

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